‘Una is a character and a story that fails to engage and the argument for its existence as a film is a sadly unsuccessful one’ ... Rooney Mara and Ben Mendelsohn in Una.

The challenge with transforming a stage production into a movie is the need to provide enough of a justification as to why the move was necessary. The differences between the two mediums and the benefits and restrictions they both provide mean that an adaptation, either way, can be fraught with difficulty. It’s even tougher when you’re dealing with a two-hander, a common theatrical construct that can feel less at home on the big screen.

David Harrower’s play Blackbird, most recently performed on stage by Jeff Daniels and Michelle Williams, is a tightly focused drama essentially based in just one room. Its big screen incarnation, from first-time director Benedict Andrews, is an attempt to expand upon this claustrophobic set-up and initially at least, it succeeds.

Una (Rooney Mara) is a young woman living in suburban middle England with her mother, haunted by a mysterious past that sees her drinking and having casual sex with strangers. She’s transfixed by a photograph of a figure from her past and it leads her to a factory where she tracks down Ray (Ben Mendelsohn), except that he’s now called Peter. He’s alarmed, angry and even frightened by the unannounced visit and we soon learn why: he sexually abused her when she was 13 and she’s convinced that they’re in love.

Aware of the inherent staginess of the material, Andrews throws in flashbacks and some nice visual flourishes to give the story a more cinematic feel and the slow-burn drama works nicely for a while. Mara and Mendelsohn have a compellingly toxic chemistry together and their initial confrontation is intriguingly tense. But once we’re locked into the meat of the story, the film has nowhere else to go, at least anywhere that’s of interest and the pace becomes laborious as their discussions turn repetitive.

Mara is as always, a self-assured and fascinating presence, but a distracting, off-key British accent jars and while she gives herself to the film, the film gives her little in return. There’s an interesting and daring conceit here, of a woman who believes that the man who sexually abused her might also be her soulmate. But the subversive victim narrative, explored with far more bite in Paul Verhoeven’s new thriller Elle, ultimately fizzles out and investment in what happens to the pair becomes increasingly difficult with attempts to de-stage the story bordering on desperate. A convoluted business sub-plot and a sorely underwritten role for the talented Riz Ahmed eventually lead to an underwhelming ending that toys with tired psycho-thriller conventions as Mara’s character becomes just another crazy woman.

There are two undeniably talented actors here and they’re matched with an initially interesting set-up but it’s not one that feels suited to the big screen, at least in this iteration. Una is a character and a story that fails to engage and the argument for its existence as a film is a sadly unsuccessful one.